## assuming the file downloaded was mysql-apt-config_0.8.19-1_all.deb and stored in your current directory
sudo dpkg -i mysql-apt-config_0.8.19-1_all.deb
## the following window will popup
## press Tab key until <Ok> is highlighted and press Enter
## update your repository
sudo apt update
## confirm that the mysql APT repository is not added to our APT sources list
sudo find /etc -name '*.list' -exec grep mysql {} \;
## The output should look like the following
# Use command 'dpkg-reconfigure mysql-apt-config' as root for modifications. deb http://repo.mysql.com/apt/ubuntu/ focal mysql-apt-config
deb http://repo.mysql.com/apt/ubuntu/ focal mysql-8.0
deb http://repo.mysql.com/apt/ubuntu/ focal mysql-tools #deb http://repo.mysql.com/apt/ubuntu/ focal mysql-tools-preview deb-src http://repo.mysql.com/apt/ubuntu/ focal mysql-8.0
## Now we are ready to install mysql-workbench-community using apt install